vldiff: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/vldiff - from package: libvcs-lite-perl

You may install the required package with command apt-get install {package}

Error in other languages:
vldiff: bevel nie gevind nie
vldiff: comandă negăsită
vldiff: comando não encontrado
vldiff: commande introuvable
vldiff: command not found
vldiff: käsku ei ole
vldiff: không tìm thấy lệnh
vldiff: komanda nerasta
vldiff: Kommando nicht gefunden.
vldiff: kommandot finns inte
vldiff: komut yok
vldiff: nie znaleziono polecenia
vldiff: níor aimsíodh an t-ordú
vldiff: no se encontró la orden
vldiff: no s'ha trobat l'ordre
vldiff: opdracht niet gevonden
vldiff: parancs nem található
vldiff: perintah tidak ditemukan
vldiff: príkaz nenájdený
vldiff: příkaz nenalezen
vldiff: команда не найдена
vldiff: командата не е открита
vldiff: 命令找不到
vldiff: コマンドが見つかりません